The present invention relates to a method for operating a self-propelled harvesting machine such as a combine harvester and a harvesting machine designed for operating according to this method.
A combine harvester typically includes a threshing step, in which a flow of harvested stalks is separated into straw, which is discarded, and into a flow that contains the threshed-out grain and contaminants such as stalk pieces, non-threshed-out ear pieces, husks, etc., and a cleaning step, in which the contaminants are removed using sieves and a blower, in order to obtain a useful-material flow composed nearly exclusively of threshed-out grain.
Contaminants that remain in this useful material make it difficult to process the grain further, which is why the yields that can be attained for inadequately cleaned grain can be much lower than the yields of well-cleaned grain.
Although it is technically easy to adjust the large number of changeable operating parameters of the threshing and cleaning step such that a highly pure useful-material flow is attained, when a set of operating parameters is optimized without compromise and solely with regard for purity-related results, high losses of useful material result. This means that, the more that contaminants in the harvested grain are suppressed, the more the amount of grain increases that is removed as residual material and is therefore not utilized, or is at least not utilized in the most economical manner. An optimal yield can therefore be attained only when a reasonable compromise is found between purity and grain loss.
It is difficult even for an experienced user to pre-select the various operating parameters that result in a useful compromise of this type, because they depend on the type of material harvested and on the environmental conditions under which the crop material has grown, e.g., ground conditions, the climate during the growing period, the moisture content of the harvested material, etc. It is therefore desirable to be able to dynamically adapt the operating parameters of a harvesting machine to the properties of the crop material.
A method is made known in DE 10147733A1, with which a harvesting machine such as a combine harvester is operated with different settings of operating parameters in succession; the combine harvester is acted upon with a quantity of crop material that remains the same, working results are obtained for the various parameter settings, and the parameter setting at which the best working result was obtained is ultimately selected. The cleanliness of the grain is a criterium for evaluating the working result.
The publication calls for the operator to carry out a subjective evaluation of the cleanliness by assigning it a rating from “adequate” to “very good”. In order to rate the cleanliness of the grain, the operator must be able to see the harvested material. This task can therefore not be carried out while the combine harvester is operating. The publication states that the cleanliness of the grain is linked to the density of the harvested grain, and that a grain density sensor can be located on a grain elevator, but it does not state how a grain density sensor of this type could be designed. It is difficult, in fact, to perform a reliable measurement of grain density of grain that moves constantly between the output of the cleaning step and the grain tank. Weighing flowing grain directly does not yield reproducible results; an indirect estimate of the density based, e.g., on optical detection, requires laborious calibration which would have to be carried out separately for every harvesting run, due to the above-mentioned environmental variables, which influence the optimum operating parameter values of the threshing and cleaning steps.